Pressure washing

[Coxie]

I was chatting to a non-caving friend about digging this morning and he said that he thought a pressure washer and a pump system to send it back out might be useful in confined spaces for removing large quantities of mud in a short space of time.


I haven't done a lot of digging and I just wondered if anyone had used this sort of thing in a dig?

 

[khakipuce]

Pumping mud can require special pumps depending on the type of mud, such as a progressive cavity pump. The fines in suspension tend to settle if not kept moving and wear the pump as they pass through. That said, the China Clay industry use water jets to extract the clay and the oil industry use bentonite "mud" to extract the debris from the hole as they drill.

Also remember that you can only "suck" a fluid up about 25 feet in elevation, anything more would need you to get the pump down to the dig, along with power.

 

[Ship-badger]

We have used a high pressure hose in a dig for many years. It is very good at moving large quantities of mud abd grit; the problem is that it "moves" it rather than "removes" it. Maybe if you had a very shallow dig you might be able to pump it out; but our dig is over 30m deep and without a power supply. It does clean the mud away, and enable us to get a better view of the rocks though.

 

[Turner]

Pumping mud can require special pumps depending on the type of mud, such as a progressive cavity pump. The fines in suspension tend to settle if not kept moving and wear the pump as they pass through. That said, the China Clay industry use water jets to extract the clay and the oil industry use bentonite "mud" to extract the debris from the hole as they drill.

Also remember that you can only "suck" a fluid up about 25 feet in elevation, anything more would need you to get the pump down to the dig, along with power.

i got a 3" 5.5hp petrol pump with 28m head, just sat about if any ones after buyin one. got it for pumping out a borehole but never used it.

 

[Cave_Troll]

is this not what the taps in Tap Passage - Peak were for?

 

[khakipuce]

i got a 3" 5.5hp petrol pump with 28m head, just sat about if any ones after buyin one. got it for pumping out a borehole but never used it.

So that would mean it can raise water 28m - i.e. the pump is at the bottom and lifts the water up. If the pump is at the top it is relying on atmospheric pressure to "push" the water up the pipe and the practical limit on that is about 25 feet. Wouldn't want to be in the same dig as a petrol pump. :yucky:

 

[Turner]

i got a 3" 5.5hp petrol pump with 28m head, just sat about if any ones after buyin one. got it for pumping out a borehole but never used it.

So that would mean it can raise water 28m - i.e. the pump is at the bottom and lifts the water up. If the pump is at the top it is relying on atmospheric pressure to "push" the water up the pipe and the practical limit on that is about 25 feet. Wouldn't want to be in the same dig as a petrol pump. :yucky:

atmospheric pressure only "pushes" things one way on my planet mate... and its not up lol.....

the pump would have to be primed, but if the 3" inlet was down to a 1" it would pull a lot easier.

as for a practical limit of 25 ft, that depends on the type + size of pump.

 

[SamT]

soz turner - but I think he's right. You are effectively creating a vacuum in the delivery pipe. Atmospheric pressure then tries to replace the vacuum by pushing the water in the well/borehole down and up the pipe, however, after about 10 meters (for water), 'cavitation' occurs where the water turns to gas, and your pump stops working/breaks.

Thats why you'll see two ratings on pump - one for how much head it can 'push' usually much greater than the distance it can 'pull' which us usually around a max of 10 meters.

 

[Brains]

yep thats about right, for mercury it is about 1000mm give or take atmospheric variation. the pump you want would be called a semi trash pump which can shift pebbles up to 50mm. trash pumps can shift boulders if you get one big enough (56"centrifugal)!

 

[Chocolate fireguard]

You are effectively creating a vacuum in the delivery pipe. Atmospheric pressure then tries to replace the vacuum by pushing the water in the well/borehole down and up the pipe, however, after about 10 meters (for water), 'cavitation' occurs where the water turns to gas, and your pump stops working/breaks.

Yes. As my old physics teacher (long gone to his rest) used to say "A vacuum IS nothing therefore a vacuum CAN DO nothing."
When my turn came to teach the subject to later generations I tried to get the idea across by pointing out that what is usually referred to as a rubber sucker should be called a rubber pusher because it`s the atmospheric pressure on the outside that pushes the device onto the wall.
They always smiled at this because it confirmed their opinion that I was just a w@^k*r.

 

[Chocolate fireguard]

yep that's about right, for mercury it is about 1000mm give or take atmospheric variation.

I think that should be 760mm of mercury or 1000millibar.
But I am just a w@^k*r.

 

[Brains]

:-[
I stand corrected - fizzix physics has never been my strongpoint, but you get the drift, milibars, milimeters, whatever... 

 

[Goydenman]

Bax and I used a pressure washer in Goyden once on a dig - it was awesome! It ripped through the mud fast. It was hard to see with the mist and mud flying. In our case the passage slpped uphill to the dig so the water and a lot of mud ran back down the passage away from the dig. Every so often we had to stop to see what progress we were making and pull back the biger stones. The only reason we stopped is that someone nicked our genny and pump from inside a locked shed